The Tories tend to be a party of low expectations. They expect the worst, even in good times, and are more than ready to criticise their leaders. This is nothing new. I can remember the criticisms made of the seven postwar Tory leaders of the opposition before David Cameron.

Tory grumblers said Winston Churchill was too old, Sir Alec Douglas-Home was too posh, Ted Heath lacked charisma, Margaret Thatcher was “Attila the Hen”, William Hague wore a funny baseball cap, Iain Duncan Smith was no leader and Michael Howard was “something of the night”. Their forebears had said worse of Baldwin in 1930, or Balfour in 1910. When I was young, old men and women could well remember the BMG (Balfour Must Go) campaign that persuaded him to retire as leader.

During the Second World War, the Government attached high importance to propaganda. We were told to “dig for victory”, that “careless talk costs lives”, that we should eat “Woolton pies”, made largely of vegetables. We were introduced to a rather tasteless fish called “snoek”.

However, the most consistent theme was that we should not be “defeatists”. The postwar publication of political diaries shows that there was a good deal of genuine defeatism among Tory MPs, not so much among their constituents. As a schoolboy, I heard little or no defeatist talk. We assumed victory.

Mr Cameron seems to remain relatively unruffled by the defeatist criticisms that have been made of him, though he sometimes shows a moderate degree of irritation, and could not be blamed for making occasional counter criticisms of his critics. It is one of the functions of a leader’s family to listen to the leader’s private view of the defeatists. Mr Cameron might well be irritated to be written off by people who seem unaware that his party won an important tactical victory this summer.

The Tories have responded to Gordon Brown’s honeymoon – a serious threat – with a summer counter-attack that has taken an October election off Mr Brown’s list of realistic options.

The Conservatives have not moved back into the lead in the late August polls, but they have moved into approximate parity. Labour and the Conservatives are both in the 35 to 39 per cent zone in public support. If Labour were at the top of that zone, and the Conservatives were at the bottom, Labour would hypothetically lead the Conservatives by 364 seats to 215 at an early general election.

That is what has been tempting Mr Brown. But if the positions were reversed, Labour, on 35 per cent of the vote, would have 301 seats, and the Conservatives, on 39, would have 282, creating a hung Parliament. In that case, Mr Brown would have given away his existing majority.

Labour did not have a large enough lead in the polls to take the big risk. The margins of error are such that a hung Parliament would be entirely possible in an early election. Before recent general elections, precampaign polls have tended to underrate both the Conservative and the Liberal Democrat shares of the actual vote, and to exaggerate Labour’s support.

It is therefore doubtful that Mr Brown could win a general election this autumn. Yet there are two emerging issues that could make it increasingly difficult for Labour to win an election postponed into 2008, or later. On October 18, which is only five weeks away, the Lisbon conference that will finalise the new European treaty will begin. Voters want a referendum on the treaty, and would probably vote “no”.

Despite occasional nervousness, the Government still seems determined to ratify by Parliament, rather than by referendum, although that would break Labour’s clear manifesto commitment from the 2005 general election. Parliamentary ratification would not be quick, or easy. Labour would have to go through a big battle, both in the Commons and the Lords, on an issue on which the Government was unpopular, but the Conservatives were strongly supported by public opinion. The Labour party is deeply split on Europe.

The other great anxiety is the economy. Mr Brown is planning reduced growth for government spending in the next three years. Already there are strikes and threats of strikes in the public sector. There can be nothing approaching the increase in spending on health and education of the late Blair years. There is also serious anxiety that the “sub-prime” banking crisis, the collapse of inter-bank lending and a collapse in the US housing market could cause a global recession.

Economic forecasting is uncertain at best; political forecasting, based on economic forecasts, amounts to uncertainty squared. Yet the uncertainty is a political factor on its own. Mr Brown ought, perhaps, to call an October general election, because he has inherited so many problems, because there are dark clouds on Europe and the global economy, because things are more likely to get worse than better. If only he could risk an October campaign many of his problems might be resolved before he had to go to the country again. But his honeymoon is already fading, the uncertainties already exist; the threat of an economic crisis is already in the newspaper headlines. Voters may suspect the motives of a Prime Minister who cut and ran after only three months in office.

Mr Cameron is an effective and tough-minded Conservative leader of liberal views. I am fairly sure that he has done well enough to make an early election too big a risk for Mr Brown to take.

If so, he may have won for the Conservatives a chance of winning the next election. They might do tolerably well in 2007; they are likely to do better in 2008, or, indeed, in 2009 or 2010. There is no call for Conservative defeatism; time may work on Mr Cameron’s side.

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